Abstract
The aim of this study was to investigate rickettsial infection in equids, opossums and ticks in the municipality of Monte Mor, a place where a Brazilian spotted fever case occurred in 2005. In addition, characteristics possibly associated with seropositivity in horses were analyzed. Serum samples from horses, mules and opossums (Didelphis albiventris) were subjected to indirect immunofluorescence assay (IFA) against Rickettsia rickettsii. The ticks collected from the animals were identified and Amblyomma sculptum ticks from the equids were tested using PCR for Rickettsia spp. Anti-R. rickettsii antibodies were detected in 22.6% (14/62) of the horses, none of the mules and 21.7% (5/23) of the opossums. Among the variables analyzed, only age > 12 years showed a statistically significant association with seropositivity among horses. All of the 166 A. sculptum ticks tested using PCR were negative. The results showed that rickettsiae of the spotted fever group was circulating in the municipality of Monte Mor when the samples were collected and indicate a need for surveillance of Brazilian spotted fever in this region.
Highlights
The genus Rickettsia consists of multiple species of obligate intracellular bacteria
The aims of this study were to investigate antibodies against R. rickettsii in horses, mules and opossums in the municipality of Monte Mor, to identify characteristics associated with seropositivity among horses and to investigate rickettsial DNA in A. sculptum ticks found in these animals
The immunofluorescence assay (IFA) test showed that 22.6% of the horses and 21.7% of the opossums were positive, which indicates that spotted fever group (SFG) rickettsiae was circulating in the municipality of Monte Mor at the time when samples were obtained
Summary
The genus Rickettsia consists of multiple species of obligate intracellular bacteria. Some of them are pathogenic to humans and animals, while others are not pathogenic or have unknown pathogenicity (Weinert et al, 2009) These bacteria have been divided into groups according to their serological or molecular profile (Raoult & Roux, 1997; Weinert et al, 2009). The spotted fever group (SFG) contains one of the most pathogenic rickettsiae in the world, Rickettsia rickettsii, which causes Brazilian spotted fever (BSF) in Brazil (Parola et al, 2013). In this country, the vectors for R. rickettsii are the ticks Amblyomma sculptum and Amblyomma aureolatum (Szabó et al, 2013). There are no studies that assessed the susceptibility of mules to R. rickettsii and their role as amplifying hosts
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